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.\" Copyright (c) 2012 The FreeBSD Foundation
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.\" This documentation was written by Pawel Jakub Dawidek under sponsorship
.\" the FreeBSD Foundation.
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.Dd March 9, 2023
.Dt CAP_FCNTLS_LIMIT 2
.Os
.Sh NAME
.Nm cap_fcntls_limit ,
.Nm cap_fcntls_get
.Nd manage allowed fcntl commands
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In sys/capsicum.h
.Ft int
.Fn cap_fcntls_limit "int fd" "uint32_t fcntlrights"
.Ft int
.Fn cap_fcntls_get "int fd" "uint32_t *fcntlrightsp"
.Sh DESCRIPTION
If a file descriptor is granted the
.Dv CAP_FCNTL
capability right, the list of allowed
.Xr fcntl 2
commands can be selectively reduced (but never expanded) with the
.Fn cap_fcntls_limit
system call.
.Pp
A bitmask of allowed fcntls commands for a given file descriptor can be obtained
with the
.Fn cap_fcntls_get
system call.
.Sh FLAGS
The following flags may be specified in the
.Fa fcntlrights
argument or returned in the
.Fa fcntlrightsp
argument:
.Bl -tag -width CAP_FCNTL_GETOWN
.It Dv CAP_FCNTL_GETFL
Permit
.Dv F_GETFL
command.
.It Dv CAP_FCNTL_SETFL
Permit
.Dv F_SETFL
command.
.It Dv CAP_FCNTL_GETOWN
Permit
.Dv F_GETOWN
command.
.It Dv CAP_FCNTL_SETOWN
Permit
.Dv F_SETOWN
command.
.El
.Sh RETURN VALUES
.Rv -std
.Sh ERRORS
.Fn cap_fcntls_limit
succeeds unless:
.Bl -tag -width Er
.It Bq Er EBADF
The
.Fa fd
argument is not a valid descriptor.
.It Bq Er EINVAL
An invalid flag has been passed in
.Fa fcntlrights .
.It Bq Er ENOTCAPABLE
.Fa fcntlrights
would expand the list of allowed
.Xr fcntl 2
commands.
.El
.Pp
.Fn cap_fcntls_get
succeeds unless:
.Bl -tag -width Er
.It Bq Er EBADF
The
.Fa fd
argument is not a valid descriptor.
.It Bq Er EFAULT
The
.Fa fcntlrightsp
argument points at an invalid address.
.It Bq Er ENOSYS
The running kernel was compiled without
.Cd "options CAPABILITY_MODE" .
.El
.Sh SEE ALSO
.Xr cap_ioctls_limit 2 ,
.Xr cap_rights_limit 2 ,
.Xr fcntl 2
.Sh HISTORY
The
.Fn cap_fcntls_get
and
.Fn cap_fcntls_limit
system calls first appeared in
.Fx 8.3 .
Support for capabilities and capabilities mode was developed as part of the
.Tn TrustedBSD
Project.
.Sh AUTHORS
This function was created by
.An Pawel Jakub Dawidek Aq Mt pawel@dawidek.net
under sponsorship of the FreeBSD Foundation.
